Conventionally, as an engine mount for supporting an engine of a motor vehicle, there has been known a structure in which a liquid is sealingly enclosed, as disclosed in, for example, Japanese Patent Kokoku (Post-Exam) Publication No. SHO-63-61533.
The conventional engine mount will be discussed below with reference to FIG. 17 and FIG. 18 hereof.
In FIG. 17, reference numeral 101 denotes an upper plate, reference numeral 102 denotes a lower plate, reference numeral 103 denotes a bolt for connecting the upper plate 101 to the engine, reference numeral 104 denotes a bearing body fixed to a vehicle body frame, reference numerals 105 and 106 denote a rubber elastic body, reference symbol R1 denotes an upper liquid chamber, reference symbol R2 denotes a lower liquid chamber, and reference numeral 107 denotes an orifice doubling as a passage connecting the upper and lower liquid chambers R1 and R2. In the manner mentioned above, a mount structure provided with both of the rubber elastic bodies 105 and 106 and the liquid chambers R1 and R2 is called as a hydro mount.
When fixing the bearing body 104 and applying a vibration in a vertical direction to the upper plate 101 via the bolt 103, the liquid stored in the upper liquid chamber R1 moves to the lower liquid chamber R2 through the orifice 107, or the liquid in the lower liquid chamber R2 moves to the upper liquid chamber R1. At this time, a vibration energy applied to the liquid is attenuated through the orifice 107. The rubber elastic bodies 105 and 106 also serve as an elastic body so as to attenuate a part of the vibration energy.
Accordingly, the vibration energy caused by the vertical vibration is attenuated by the liquid and the rubber elastic body. This is a basic operation of the hydro mount.
In FIG. 18, reference symbol R3 denotes a left liquid chamber, reference symbol R4 denotes a right liquid chamber, reference numeral 108 denotes an outer ring, and reference numeral 109 denotes a communication pore formed in the rubber elastic body 105 in such a manner as to extend along an inner surface of the outer ring 108.
When fixing the bearing body 104 and applying a vibration in a lateral direction to the upper plate 101 via the bolt 103, the liquid stored in the left liquid chamber R3 moves to the right liquid chamber R4 through the transfer pore 109, or the liquid in the right liquid chamber R4 moves to the left liquid chamber R3. At this time, a vibration energy applied to the liquid is attenuated through the transfer pore 109. The rubber elastic bodies 105 and 106 also serve as an elastic body so as to attenuate a part of the vibration energy.
Since the hydro mount described in Publication No. SHO-63-61533 mentioned above attenuates not only the vertical vibration but also the lateral vibration, it is preferable for the engine mount. However, in order to form the left and right liquid chambers R3 and R4, and the transfer pore 109, a high degree of manufacturing technique is required. Further, since a shape is as a whole complex, an outer diameter is increased and a size is increased as a whole, in order to arrange the left and right liquid chambers R3 and R4 having a fixed volume.
In addition, since the transfer pore 109 is long, it is considered that a cross sectional area changes due to deterioration of rubber generated by a long term use or the like. When the cross sectional area changes, a throttling characteristic changes. Accordingly, the hydro mount of Publication No. SHO-63-61533 has a drawback in terms of durability.